Former South Carolina Gov. Mark Sanford said Thursday night he “failed very publicly” when he revealed an extramarital affair in 2009, but has learned from his missteps.

“My faults are out and they are exposed,” the Republican said during a campaign debate. “But all I can say is that I have learned mightily from every one of those mistakes.”

Sanford disappeared for a week in June 2009 when he was governor, telling his staff he was hiking the Appalachian Trail when in fact he was visiting his mistress, to whom he is now engaged, in Argentina. He later apologized for being unfaithful to his wife.

Sanford served out the rest of his term and is now vying with Curtis Bostic, a former Charleston County Council member, for the GOP nomination in a special election for the U.S. House seat that the former governor held nearly two decades ago.

Sanford said his ability to confront his flaws brings “a level of humility that frankly is desperately needed in Washington, D.C.,” The Washington Post reported.

Bostic countered that Sanford would not be a strong candidate in the general election against Democratic nominee Elizabeth Colbert Busch, saying, “Trust is not had. … A compromised candidate is not what we need.”

Bostic has the support of many Christian conservatives, including former presidential candidate Rick Santorum, who campaigned for him on Wednesday.

But Bostic came in well behind Sanford in last week’s primary, although the former governor failed to win a majority of the vote. Sanford’s failure to break 50 percent of the vote triggered next Tuesday’s runoff election with Bostic.